1. Field of the Invention
The present invention relates to a wireless communications unit, a wireless communications method, a wireless communications system, and a computer program.
2. Description of the Related Art
A method is generally known by which a communications unit transmits data through a serial bus transmission route that is defined by the Universal Serial Bus (USB) specification. Recently, the Wireless USB specification has been defined as a method for wirelessly transmitting and receiving the data that is transmitted through the serial bus transmission route.
In the Wireless USB specification, the USB host assigns a unique USB address to a USB device in the following manner. First, the USB device, using a general-purpose address, requests the USB host to assign an address. The USB host responds to the request and assigns a temporarily valid, for example, unauthenticated address, to the USB device. Then, after the USB host authenticates the USB device, it exchanges prescribed information with the USB device, then assigns a Wireless USB device address to the USB device (see Universal Serial Bus (http://www.usb.org/developers/wusb/)).
Note that the Alliance Distributed Media Access Control specifications (hereinafter called simply the “WiMedia specifications”) are defined as the Ultra-Wideband (UWB) wireless communications specifications that use Wireless USB.
According to the WiMedia specifications, the USB device transmits in a beacon slot a beacon that includes the USB device's address at the current time, as well as reservation information pertaining to a time slot that the USB device will use. After the USB device transmits the beacon, it is allowed to transmit and receive data in the time slot. Here, a configuration in which each USB device transmits the beacon in the beacon slot is used so that all the USB devices will coexist in an autonomous distributed network.